In the use of conventional polyurethane foam providing apparatus, the foam constituents, namely polyisocyanate and polyol, were brought together in a mixing head wherein they were then projected into a suitable mold. Prior art mixing heads such as disclosed in Reichert, U.S. Pat. No. 3,306,540, granted Feb. 28, 1967, and Hansen et al, U.S. Pat. No. 3,111,389, granted Nov. 19, 1963, were of heavy duty construction which generally required stationary support structures.
It was desired in the prior art to provide a foam gun which could be hand-held. Hand-held guns were common with fluid sprays such as shown in New, U.S. Pat. No. 3,318,535, granted May 9, 1967. However, the design of polymerizable polyurethane foam guns provided difficulties not encountered in conventional spray guns, in that the foam was unusually laminar in flow and would also tend to polymerize within the gun structure. Diverse and unwieldy piping, valving, and mixing elements were generally required, which precluded practical hand gun designs. Complex construction such as shown in Armeniades et al, U.S. Pat. No. 3,286,992, granted Nov. 27, 1966, were often necessarily used for mixing viscous resins.
One approach to a form gun design was to use a high pressure (i.e. up to 800 psi) air actuated rod that retracts to uncover opposing polyioscyanate and polyol feeds, wereby the air agitates the opposing feed streams. Such devices required extremely high pressures, with disruptive flow patterns, and were generally difficult and costly to manufacture, operate and maintain.
Now there is provided by the present invention a foam gun which is of simplified, positive acting construction.
It is therefore a principal object of this invention to provide an improved foam gun, particularly useful for polyurethane foams.
It is another object of this invention to provide a polyurethane foam gun of simplified construction which is readily manufactured and operated.
It is a further object of this invention to provide a polyurethane foam gun in which there is improved flow pattern and mixing with moderate fluid pressure requirements.
It is a further object of this invention to provide a polyurethane foam gun which may be readily flushed to avoid ingun polymerization.
It is a further object of this invention to provide a polyurethane foam gun wherein the operating mechanisms are mounted on the gun itself.
It is a further object of this invention to provide a polyurethane foam gun with improved nozzle mixing.
It is a further object of this invention to provide a polyurethane foam gun which is readily fabricated of molded piece construction.
It is a further object of this invention to provide a polyurethane foam gun which is practical in design, light-weight, and yet safe and practical in use.